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Abstract:

A method of producing an infrared light-reflecting film includes a
coating step of coating a polymerizable liquid crystal composition
including a polymerizable cholesteric liquid crystal compound (A), a
chiral agent having an HTP of 50 μm-1 or less (B), a
monofunctional monomer (C), and an organic solvent (D) on a substrate, an
alignment step of aligning the polymerizable cholesteric liquid crystal
compound by heating to form a cholesteric liquid crystal phase, and an
irradiation step of irradiating the polymerizable liquid crystal
composition with actinic radiation to fix the cholesteric liquid crystal
phase and form an infrared light-reflecting layer, wherein the amount of
a residual solvent after the alignment step is controlled to 0.20
g/m2 or more.

Claims:

1. A method of producing an infrared light-reflecting film, comprising: a
coating step of coating a polymerizable liquid crystal composition
including a polymerizable cholesteric liquid crystal compound (A), a
chiral agent having an HTP represented by the following Expression (1) of
50 μm-1 or less (B), a monofunctional monomer (C), and an organic
solvent (D) on a substrate, an alignment step of aligning the
polymerizable cholesteric liquid crystal compound by heating to form a
cholesteric liquid crystal phase, and an irradiation step of irradiating
the polymerizable liquid crystal composition with actinic radiation to
fix the cholesteric liquid crystal phase and form an infrared
light-reflecting layer, wherein the amount of a residual solvent after
the alignment step is controlled to 0.20 g/m2 or more,
HTP=Refractive Index of Polymerizable Cholesteric Liquid Crystal
Compound/{Selective Reflection Wavelength (unit: μm) of Cholesteric
Liquid Crystal Phase×Mass ratio of Chiral Agent to Polymerizable
Cholesteric Liquid Crystal Compound}. Expression (1)

2. The method of producing an infrared light-reflecting film according to
claim 1, wherein the organic solvent (D) includes at least two kinds of
organic solvent.

3. The method of producing an infrared light-reflecting film according to
claim 1, wherein the organic solvent (D) includes an organic solvent
having a boiling point of 150.degree. C. or higher.

4. The method of producing an infrared light-reflecting film according to
claim 3, wherein the proportion of the organic solvent having a boiling
point of 150.degree. C. or higher with respect to the total amount of the
organic solvent (D) is not less than 3% by mass and not more than 30% by
mass.

5. The method of producing an infrared light-reflecting film according to
claim 3, wherein the organic solvent (D) is a compound having a
hydrocarbon ring of a 6- to 7-membered ring.

6. The method of producing an infrared light-reflecting film according to
claim 1, wherein the monofunctional monomer (C) is a (meth)acrylate
compound.

7. The method of producing an infrared light-reflecting film according to
claim 1, wherein the addition amount of the monofunctional monomer (C)
with respect to the total mass of the polymerizable cholesteric liquid
crystal compound (A) and the monofunctional monomer (C) in the
polymerizable liquid crystal composition is from 2% by mass to 30% by
mass.

8. The method of producing an infrared light-reflecting film according to
claim 1, wherein the addition amount of chiral agent (B) with respect to
the total mass of the polymerizable cholesteric liquid crystal compound
(A) and the monofunctional monomer (C) in the polymerizable liquid
crystal composition is from 1% by mass to 18% by mass.

9. The method of producing an infrared light-reflecting film according to
claim 1, wherein the HTP of the chiral agent (B) is 40 μm-1 or
less.

10. The method of producing an infrared light-reflecting film according
to claim 1, wherein a photopolymerization initiator is added to the
polymerizable liquid crystal composition.

11. The method of producing an infrared light-reflecting film according
to claim 1, wherein the infrared light-reflecting layer reflects infrared
light at a wavelength of 800 nm or more.

12. The method of producing an infrared light-reflecting film according
to claim 1, wherein the infrared light-reflecting layer reflects
left-handed circularly polarized light.

13. The method of producing an infrared light-reflecting film according
to claim 1, further comprising: a laminating step of laminating two or
more infrared light-reflecting layers by repeating at least once a set of
the coating step using the other kind of the polymerizable liquid crystal
composition on the infrared light-reflecting layer, the alignment step,
and the irradiation step.

14. The method of producing an infrared light-reflecting film according
to claim 13, wherein the infrared light-reflecting layer has at least one
layer of each of a layer reflecting right-handed circularly polarized
light and a layer reflecting left-handed circularly polarized light.

15. The method of producing an infrared light-reflecting film according
to claim 13, wherein at least one of the infrared light-reflecting layers
reflects infrared light at a wavelength of 800 nm or more.

16. The method of producing an infrared light-reflecting film according
to claim 1, wherein the substrate is a polyethylene terephthalate film.

17. The method of producing an infrared light-reflecting film according
to claim 1 for producing an infrared light-reflecting film for a window
member of a vehicle or a window member of a building structure.

18. An infrared light-reflecting film produced by the method of producing
an infrared light-reflecting film according to claim 1.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an infrared light-reflecting film
that has a layer formed by fixing a cholesteric liquid crystal phase, and
a production method thereof.

[0003] 2. Description of the Related Art

[0004] With the recent increase of concern over and interest in the
environment or energy, energy-saving industrial products have been
increasingly demanded. For example, glass and films have been required
which could effectively shield glass windows of houses or vehicles from
heat, that is, effectively reduce the thermal load due to solar rays. In
order to reduce the thermal load due to solar rays, it is necessary to
prevent the transmission of some solar rays in the visible light region
or the infrared light region in a solar light spectrum. Particularly,
from the viewpoint of safety, high transmittance to the visible light
region and heat-shielding performance are actively required for vehicle
windows, and the reflectance of solar rays tends to be regulated in some
countries.

[0005] Multi-layered glass coated with a special metal film blocking heat
radiation, which is called low-E double glazing, is frequently used as
eco-glass having high heat-insulating performance or high heat-shielding
performance. The special metal film can be produced by laminating plural
layers, for example, by the use of a vacuum film-forming method. The
coating of the special metal film produced by the use of the vacuum
film-forming method is excellent in reflection performance, but the
vacuum process is low in productivity, whereby the production cost
thereof is high. When a metal film is used, there is a problem, for
example, in that electromagnetic waves are also shielded to cause radio
interference when using mobile phones or the like, and in that when the
metal film is used for vehicles, use of ETC (Electronic Toll Collection
System) may be prevented. High transmittance of visible rays is required
as well as resistance to the radio interference for vehicle windows in
view of safety.

[0006] In this regard, a method using a cholesteric liquid crystal phase
has been proposed. For example, JBP4109914B discloses a laminated optical
film having a reflective circularly-polarizing plate formed thereon,
which is arranged so as to allow penetration of the circularly polarized
light in the same direction to both surfaces of a cholesteric liquid
crystal phase.

[0007] Furthermore, JP2009-514022A (JP-H21-514022A) discloses an infrared
light-reflecting article having a cholesteric liquid crystal phase. In
addition, JP3500127B discloses an embodiment in which plural layers of
the cholesteric liquid crystal phase are laminated in order to provide a
use in a liquid crystal display device of reflecting light in the visible
light region efficiently.

[0008] In laminating plural cholesteric liquid crystal phase layers, for
example, a method of drying, heat-orienting, and UV-curing of a coating
film containing a cholesteric liquid crystal material and repeating the
above steps to laminate a cholesteric liquid crystal phase layer by layer
on the previously formed cholesteric liquid crystal phase is used.
Regarding the method of curing a cholesteric liquid crystal phase, a
method of applying UV rays to a polymerizable liquid crystal is generally
used, for example, as disclosed in JP4008358B. JP4008358B discloses a
method of producing a cholesteric liquid crystal film of which the
reflection wavelength band is wide by adjusting the illumination
intensity in a predetermined range. JP3745221B discloses a method of
producing a polarizer in which the wavelength region is continuous by
setting the rotation directions of liquid crystal molecules in each of
cholecteric liquid crystal phases to be identical at the time of
laminating the cholesteric liquid crystal phases.

[0009] Furthermore, steps for coating and drying a liquid crystal material
are disclosed in various documents. For example, JP2007-502911A discloses
a method in which a liquid crystal composition including a cholesteric
liquid crystal compound and 1,3-dioxolane is coated on a substrate and
the initial drying condition is adjusted to form a cholesteric liquid
crystal phase. JP2010-128270A discloses a method for producing an optical
compensation film by adjusting the boiling point of an organic solvent,
the phase transfer temperature of a liquid crystal compound, and the
temperature in the temperature-raising and drying step. JP2010-128270A
notes that it is preferable to reduce the amount of the residual solvent
in a coating film to a range of 0.20 g/m2 or less range before the
step of aligning a liquid crystal compound. In JP2005-121827A, a phase
difference plate having a uniform retardation is produced by using a
solvent having a boiling point of 90° C. or higher and 250°
C. or lower as a composition component.

SUMMARY OF THE INVENTION

[0010] In order to produce a light-reflecting film having high
heat-shielding performance, it is necessary to reduce the haze of a film
and control the reflection wavelength band with a good precision. In
order to reflect light at a long wavelength (in an infrared light region)
by controlling the reflection wavelength band, a chiral agent is
generally added, while adjusting the concentration, to a liquid crystal
compound (for example, a rod-shaped liquid crystal compound) exhibiting a
cholesteric liquid crystal phase, and the reflection band is adjusted. In
this case, qualitatively, it is necessary to reduce the amount of the
chiral agent added in order to shift the reflection wavelength to a long
wavelength side (to the infrared light region).

[0011] Furthermore, in order to reduce the haze of a film, it is necessary
to improve the alignment property of the cholesteric liquid crystal
phase. This makes it possible to eliminate the alignment defects of the
light-reflecting film and to adjust the haze to be lower.

[0012] HTP is generally used as an indicator indicating the performance of
a chiral agent. HTP is an abbreviation of Helical Twisting Power and is a
factor indicating the helically aligning ability expressed by Expression
(1) below. Specifically, refer to "Study of Photosensitive Chiral
Compounds for Cholesteric Liquid Crystals Directed toward the Color
Filter for Liquid Crystal Display" (Masatoshi Yumoto and Mitsuyoshi
Ichihashi, Fuji Film Research Report No. 50 (2005), pp. 60-63).

[0013] Therefore, it is preferable to adjust the reflection wavelength
using a small amount of a chiral agent having a high HTP in order to
shift a reflection wavelength to a long wavelength side to reflect
infrared light and to produce a light-reflecting film having a superior
alignment property.

[0014] However, since no chiral agent causing left-handed twisting has a
high HTP, it is inevitable at present to use a chiral agent having a low
HTP. It is necessary to increase the amount of the chiral agent to be
added so as to attain a desired reflection wavelength using such a chiral
agent having a low HTP. As a result, the content of the impurities in the
cholesteric liquid crystal phase is increased and the alignment property
of the cholesteric liquid crystal is deteriorated, which causes a problem
of an increase in the haze of the light-reflecting film.

[0015] In addition, in order to produce a cholesteric liquid crystal
phase, it is also required to add a monofunctional monomer to improve the
brittleness of a film. Similarly, in this case, the content of impurities
in the cholesteric liquid crystal phase is increased and the alignment
property of the cholesteric liquid crystal is deteriorated, which causes
a problem of an increase in the haze of the light-reflecting film.

[0016] Therefore, it is strongly desired to produce an infrared
light-reflecting film having excellent brittleness and a good haze even
when a chiral agent having a low HTP is used.

[0017] It is an object to be attained by the invention to provide a method
for producing an infrared light-reflecting film, by which an infrared
light-reflecting film having excellent brittleness and a good haze even
when a chiral agent having a low HTP is used can be obtained.

[0018] The present inventors have conducted extensive studies in order to
solve the above-described problems, and as a result, they have found that
the above-described problems can be solved by increasing the amount of
the residual solvent under a specific condition in the step of aligning
the liquid crystal compound even when using a chiral agent having a low
HTP or monofunctional monomers, which may gives an adverse effect on the
alignment of the liquid crystal, in contrast to the findings from
JP2010-128270A.

[0019] The method of producing an infrared light-reflecting film of the
invention obtained by solving the above-described problems includes a
coating step of coating a polymerizable liquid crystal composition
including a polymerizable cholesteric liquid crystal compound (A), a
chiral agent having an HTP represented by the following Expression (1) of
50 μm-1 or less (B), a monofunctional monomer (C), and an organic
solvent (D) on a substrate, an alignment step of aligning the
polymerizable cholesteric liquid crystal compound by heating to form a
cholesteric liquid crystal phase, and an irradiation step of irradiating
the polymerizable liquid crystal composition with actinic radiation to
fix the cholesteric liquid crystal phase and form an infrared
light-reflecting layer, wherein the amount of a residual solvent after
the alignment step is controlled to 0.20 g/m2 or more.

[0020] In a preferable embodiment of the invention, the organic solvent
(D) includes at least two kinds of organic solvent, the organic solvent
(D) includes an organic solvent having a boiling point of 150° C.
or higher, the proportion of the organic solvent having a boiling point
of 150° C. or higher to the total amount of the organic solvent
(D) is not less than 3% by mass and not more than 30% by mass, or the
organic solvent (D) is a compound having a hydrocarbon ring in the form
of a 6- to 7-membered ring.

[0021] Furthermore, in a preferable embodiment of the invention, the
monofunctional monomer (C) is a (meth)acrylate compound, the addition
amount of the monofunctional monomer (C) with respect to the total mass
of the polymerizable cholesteric liquid crystal compound (A) and the
monofunctional monomer (C) in the polymerizable liquid crystal
composition is from 2% by mass to 30% by mass, or the addition amount of
chiral agent (B) with respect to the total mass of the polymerizable
cholesteric liquid crystal compound (A) and the monofunctional monomer
(C) in the polymerizable liquid crystal composition is from 1% by mass to
18% by mass.

[0022] Moreover, in a preferable embodiment of the invention, the HTP of
the chiral agent (B) is 40 μm-1 or less, but in a preferable
embodiment, a photopolymerization initiator is added to the polymerizable
liquid crystal composition, the infrared light-reflecting layer reflects
infrared light at a wavelength of 800 nm or more, or the infrared
light-reflecting layer reflects left-handed circularly polarized light.

[0023] Furthermore, in a preferable embodiment of the invention, a
laminating step of laminating two or more infrared light-reflecting
layers by repeating at least once a set of the coating step using the
other kind of the polymerizable liquid crystal composition on the
infrared light-reflecting layer, the alignment step, and the irradiation
step is included, the infrared light-reflecting layer has at least one
layer of each of a layer reflecting right-handed circularly polarized
light and a layer reflecting left-handed circularly polarized light, at
least one of the infrared light-reflecting layers reflects infrared light
at a wavelength of 800 nm or more, or the substrate is a polyethylene
terephthalate film.

[0024] In a preferable embodiment, the method of producing an infrared
light-reflecting film of the invention is a method for producing an
infrared light-reflecting film for window members of vehicles or window
members of building structures.

[0025] In the invention, an infrared light-reflecting film produced by the
method for producing an infrared light-reflecting film above is also
included.

[0026] According to the invention, a method of producing an infrared
light-reflecting film, by which an infrared light-reflecting film having
excellent brittleness and a good haze can be obtained even when a chiral
agent having a low HTP is used, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a cross-sectional view schematically illustrating an
example of the infrared light-reflecting film produced by a production
method according to the invention.

[0028] FIG. 2 is a cross-sectional view schematically illustrating another
example of the infrared light-reflecting film produced by the production
method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, the invention will be described in detail. The
description of the constitution requirements below may be based on the
representative embodiments of the invention, but the invention is not
intended to be limited to such embodiments. Further, in the present
specification, a range of numerical values represented using "to" means a
range that includes the numerical values described before and after the
"to" as a minimum value and a maximum value. In addition, in the present
specification, the polymerizable group refers to a group which causes a
polymerization reaction by irradiation with actinic radiation.

[0030] [Method of Producing Infrared Light-Reflecting Film]

[0031] The method for producing an infrared light-reflecting film of the
invention includes a coating step of coating a polymerizable liquid
crystal composition including a polymerizable cholesteric liquid crystal
compound (A), a chiral agent having an HTP represented by the following
Expression (1) of 50 μm-1 or less (B), a monofunctional monomer
(C), and an organic solvent (D) on a substrate, an alignment step of
aligning the polymerizable cholesteric liquid crystal compound by heating
to form a cholesteric liquid crystal phase, an irradiation step of
irradiating the polymerizable liquid crystal composition with actinic
radiation to fix the cholesteric liquid crystal phase and form an
infrared light-reflecting layer, wherein the amount of the residual
solvent after the alignment step is controlled to 0.20 g/m2 or more.
Herein, the HTP is a value represented by the following Expression (1).
Further, the method of producing an infrared light-reflecting film of the
invention may also be referred to the production method of the invention.

[0034] The helical alignment power of a chiral agent can be expressed by
HTP (Helical Twisting Power). Here, the refractive index of a curable
liquid crystal compound in Expression (1) means the following, for
example, as described in page 20 of "Lightwave Engineering (Yasuo
Kokubun, published by Kyoritsu Publishing Co. (1999)".

[0035] The selective reflection wavelength of the cholesteric liquid
crystal phase means a wavelength obtained by multiplying the average
refractive index of the cholesteric liquid crystal molecules with the
chiral pitch (helical pitch) of the cholesteric liquid crystal molecules.
The mass ratio of the chiral agent to the polymerizable cholesteric
liquid crystal compound means a ratio of solid mass (weight) of the
chiral agent per unit/mass (weight) of the polymerizable cholesteric
liquid crystal compound per unit. A higher HTP means a higher helically
aligning ability, and is capable of allowing production of a film having
a low haze, which is thus preferable. However, since no chiral agent
causing left-handed twisting causes a high HTP, it is required at present
to use a chiral agent having a low HTP. Accordingly, in the invention, a
chiral agent having a low HTP is used.

[0036] The HTP of the chiral agent used in the invention is 50
μm-1 or less, preferably 45 μm-1 or less, and
particularly preferably 40 μm-1 or less. Further, the HTP of the
chiral agent is preferably 10 μm-1 or more, and more preferably
20 μm-1 or more.

[0037] Here, the HTP of the chiral agent can be determined by
experimentally acquiring the dependency of a selective wavelength on the
chiral agent concentration and can be determined uniquely.

[0038] (Reflection Wavelength)

[0039] The production method of the invention relates to a method of
producing an infrared light-reflecting film. By using the production
method of the invention, an infrared light-reflecting film having
excellent brittleness and a good haze can be obtained even when a chiral
agent having a low HTP is used. Further, it is known that a wavelength in
a specific region, that is reflected by the infrared light-reflecting
film, can be shifted according to various factors of the production
method. For example, the wavelength region that can be reflected may be
shifted by adjusting the conditions such as the concentration of the
chiral agent to be added, the temperature at which the cholesteric liquid
crystal phase is fixed, the irradiance or the irradiation time, and the
like. Further, the wavelength region that can be reflected as mentioned
herein is the same as the selective reflection wavelength in the
Expression (1).

[0040] The method for producing an infrared light-reflecting film of the
invention can be preferably used in the case of production of an infrared
light-reflecting film that reflects the infrared light at 800 nm or more.

[0041] The production method of the invention is accomplished by the
finding that when using a chiral agent having a low HTP, and a
monofunctional monomer so as to improve the brittleness, and further,
when an infrared light-reflecting layer reflecting a wavelength in the
long-wavelength infrared light region is used, the chiral agent or the
monofunctional monomer gives an effect on the alignment of the liquid
crystal and thus deteriorates the haze of a film. The production method
of the invention can solve the above-described problems by controlling
the amount of the residual solvent after the alignment step within a
specific range.

[0042] The production method of the invention can be preferably used for
production of an infrared light-reflecting film having a reflection
center wavelength in 950 to 2000 nm, and more preferably used for
production of an infrared light-reflecting film having a reflection
center wavelength in 950 to 1400 nm. Further, the reflection center
wavelength as mentioned herein is calculated by λ=npitch (in the
formula, n represents an average refractive index of the liquid crystal,
and the pitch represents the helical pitch (nm) of the cholesteric liquid
crystal), but the half-width of the reflection spectrum may be simply
referred to as a reflection center wavelength.

[0043] (Production Step)

[0044] Hereinbelow, the materials or steps that are preferably used in the
method of producing an infrared light-reflecting film of the invention
will be sequentially described. First, each of the production steps that
are preferably used in the invention will be described.

[0045] Coating Step:

[0046] The production method of the invention includes a coating step of
coating a polymerizable liquid crystal composition including a
polymerizable cholesteric liquid crystal compound (A), a chiral agent
having an HTP represented by the following Expression (1) of 50
μm-1 or less (B), a monofunctional monomer (C), and an organic
solvent (D) on a substrate.

[0047] The polymerizable liquid crystal composition is preferably prepared
by dissolving and/or dispersing the materials into the organic solvent
(D). In the production method of the invention, it is preferable that a
photopolymerization initiator be added to the polymerizable liquid
crystal composition.

[0048] In the coating step of the invention, the polymerizable liquid
crystal composition is finished into a coating liquid, and is preferably
coated on a surface of a substrate such as polymer film, a glass plate, a
quartz plate, and the like, or, if necessary, to a surface of an
alignment layer formed on the substrate. The polymerizable liquid crystal
composition can be coated according to various methods of a wire bar
coating method, an extrusion coating method, a direct gravure coating
method, a reverse gravure coating method, a die coating method, and the
like.

[0049] Drying Step:

[0050] The production method of the invention may further include a drying
step of drying the coated polymerizable liquid crystal composition, in
addition to the coating step, the alignment step, and the irradiation
step. The drying step may be carried out at any time, or preferably
carried out after the coating step, and more preferably after the coating
step and before the alignment step. Further, the drying step can be
carried out without limitation by heating, blowing air, or other methods,
but it is preferably carried out by heating at 10° C. to
60° C. for 5 seconds to 600 seconds, more preferably at 15°
C. to 55° C. for 5 seconds to 200 seconds, particularly preferably
at 20° C. to 50° C. for 10 seconds to 100 seconds.

[0051] The amount of the residual solvent after the drying step, that can
be used in the invention, is preferably controlled to 0.25 g/m2 or
more and 1.5 g/m2 or less, more preferably to 0.3 g/m2 or more
and 1.2 g/m2 or less, and particularly preferably to 0.4 g/m2
or more and 1.0 g/m2 or less. The amount of the residual solvent
after the drying step can be calculated in the following manner.

(Amount of Residual Solvent after Drying Step)=(Mass after Drying
Step)-(Mass after Drying at 130° C./30 minutes)

[0052] In addition, as a method for controlling a range of the amount of
the residual solvent after the drying step, a method such as a method for
controlling the amount of the residual solvent after the alignment step
as described below can be preferably used.

[0053] Alignment Step:

[0054] The production method of the invention includes a step in which the
coated polymerizable liquid crystal composition is heated to align the
polymerizable cholesteric liquid crystal compound to form a state of a
cholesteric liquid crystal phase.

[0055] In order to set a transition temperature to form the cholesteric
liquid crystal phase, the coated polymerizable liquid crystal composition
is heated. As a heating method, for example, the coating film is once
heated up to the temperature of the isotropic phase, and then cooled to
the cholesteric liquid crystal phase transition temperature, whereby the
film may stably have the intended cholesteric liquid crystal phase. The
liquid crystal transition temperature of the curable liquid crystal
composition is preferably within a range of from 10 to 250° C.
from the viewpoint of the production aptitude, and more preferably within
a range of from 10 to 150° C. With the temperature of 10°
C. or higher, it is easy to adjust the temperature to a temperature range
exhibiting the liquid crystal phase, whereas the temperature of
200° C. or lower is preferable from the viewpoints of consumption
of heat energy or the like, and is advantageous in view of deformation,
degradation, or the like of the substrate.

[0056] In order to align the polymerizable cholesteric liquid crystal
compound to form a state of a cholesteric liquid crystal phase, it is
preferable to heat the compound at 50° C. to 150° C. for 5
seconds to 600 seconds, more preferably at 70° C. to 130°
C. for 5 seconds to 480 seconds, and particularly preferably at
80° C. to 100° C. for 30 seconds to 300 seconds.

[0057] In the invention, the amount of the residual solvent after the
alignment step is controlled to 0.20 g/m2 or more.

[0058] The amount of the residual solvent after the alignment step can be
measured by means of an analysis balance XP205 (manufactured by METTLER
TOLEDO International Inc.), and calculated by the following formula.

(Amount of Residual Solvent after Alignment Step)=(Mass after Alignment
Step)-(Mass after Drying at 130° C./30 Minutes)

[0059] In addition, examples of the method for controlling a range of the
amount of the residual solvent after the alignment step include use of
the following types of organic solvents or a combination thereof.

[0060] The amount of the residual solvent after the alignment step of the
invention is preferably controlled to 0.20 g/m2 or more and 0.50
g/m2 or less, more preferably 0.23 g/m2 or more and 0.40
g/m2 or less, and particularly preferably 0.26 g/m2 or more and
0.33 g/m2 or less.

[0061] The mechanism with which an infrared light-reflecting film having
excellent brittleness and a good haze can be obtained by controlling the
amount of the residual solvent after the alignment step in the invention
to 0.20 g/m2 or more even when a chiral agent having a low HTP and
monofunctional monomer is used is not sufficiently clarified, but the
present inventors have speculated as follows. Since the amount of the
residual solvent in the liquid crystal film during the liquid crystal
alignment step is large, the viscosity of the liquid crystal film is
lowered and the liquid crystal in the liquid crystal film easily moves,
and accordingly, is easily helically aligned. Further, the monofunctional
monomer moves between the polymerizable liquid crystals and is
polymerized, portions having broken network in places are generated,
which have a rubber-like action. Thus, it is thought that the film is
easily stretched and the brittleness is improved. It is thought that by
the above action, the effect of the invention can be obtained. However,
the invention is not limited to the mechanism above.

[0062] Irradiation Step:

[0063] The production method of the invention includes an irradiation step
in which the polymerizable liquid crystal composition is irradiated with
actinic radiation to fix the cholesteric liquid crystal phase and form an
infrared light-reflecting layer.

[0064] As the actinic radiation, ultraviolet rays or the like can be used.
When irradiation with ultraviolet rays is used, a light source such as an
ultraviolet ray lamp and the like is used. In this step, by irradiation
with ultraviolet rays, the cholesteric liquid crystal phase is fixed, and
the infrared light-reflecting layer is formed.

[0065] The energy amount with irradiation of actinic radiation is not
particularly limited, but is generally from about 100 mJ/cm2 to 800
mJ/cm2. Further, the time for irradiating the polymerizable liquid
crystal composition with actinic radiation is not particularly limited,
but is determined from the viewpoints of sufficient strength of a cured
film (infrared light-reflecting layer) and productivity.

[0066] In order to promote the reaction for fixing the cholesteric liquid
crystal phase, irradiation with actinic radiation under a heating
condition may be carried out. Further, it is preferable to maintain the
temperature during irradiation with actinic radiation to a temperature
range showing the cholesteric liquid crystal phase and not so as to
deform the cholesteric liquid crystal phase. In addition, the oxygen
concentration under a curing reaction atmosphere is involved in the
degree of polymerization. For this reason, a desired degree of
polymerization is not attained with a curing reaction in air, and when
the film strength is not sufficient, it is preferable to lower the oxygen
concentration under the curing reaction atmosphere by a method such as
nitrogen replacement and the like. As a desirable oxygen concentration,
it is preferably 10% by volume or less, more preferably, more preferably
7% by volume or less, and most preferably 3% by volume or the less.

[0067] In the irradiation step, the cholesteric liquid crystal phase is
fixed and an infrared light-reflecting layer is formed. Herein, the state
in which the liquid crystal phase is "fixed" is most usually a state in
which the alignment of the liquid crystal compound made of the
cholesteric liquid crystal phase is maintained, and in a preferable
embodiment, it is not limiting. Specifically, in a temperature range of
usually 0° C. to 50° C., or under a more stringent
condition of -30° C. to 70° C., the state means a state in
which the fixed alignment morphology can be stably maintained while the
infrared light-reflecting layer is not flowable and the alignment
morphology is not caused to be changed by an external field or external
force. In the invention, the alignment state of the cholesteric liquid
crystal phase is fixed by irradiation with actinic radiation.

[0068] Further, in the invention, the optical properties of the
cholesteric liquid crystal phase are sufficient as long as they are
maintained in the infrared light-reflecting layer, and it is not
necessary that the liquid crystal composition in the infrared
light-reflecting layer exhibit a liquid crystal property consequently.
For example, the liquid crystal composition may have a high molecular
weight due to a curing reaction and thus lose the liquid crystal
property.

[0069] Lamination Step:

[0070] The production method of the invention preferably includes a
laminating step of laminating two or more (more preferably three or more)
infrared light-reflecting layers by repeating at least once a set of the
coating step using the other kind of the polymerizable liquid crystal
composition on the infrared light-reflecting layer, the alignment step,
and the irradiation step. The production method of the invention can also
be preferably employed in the case of obtaining a laminate having three
or more infrared light-reflecting layers above.

[0071] (Materials)

[0072] Next, the materials that can be used in the production method of
the invention will be described. In the production method of the
invention, the polymerizable cholesteric liquid crystal compound (A), the
chiral agent having an HTP represented by the Expression (1) of 50
μm1 or less (B), the monofunctional monomer (C), and the organic
solvent (D) are used.

[0073] Furthermore, in the production method of the invention, an
alignment control agent is preferably included from the viewpoint of
obtaining a good alignment property. Further, in the production method of
the invention, a polymerization initiator is preferably included.

[0074] Polymerizable Cholesteric Liquid Crystal Compound:

[0075] The polymerizable liquid crystal composition that is used in the
method of the invention includes a polymerizable cholesteric liquid
crystal compound.

[0076] The polymerizable cholesteric liquid crystal compound may be
rod-shaped or disc-shaped, but it is preferably rod-shaped.

[0078] In the production method of the invention, the polymerizable liquid
crystal composition is one exhibiting a cholesteric liquid crystal phase,
and the polymerizable liquid crystal composition includes at least one
kind of polymerizable cholesteric liquid crystal compound.

[0079] The polymerizable cholesteric liquid crystal compound can be
obtained by introducing a polymerizable group into the cholesteric liquid
crystal compound. Examples of the polymerizable group include an
unsaturated polymerizable group, an epoxy group, and an aziridinyl group,
and an unsaturated polymerizable group is preferable; and an ethylene
unsaturated polymerizable group is particularly preferable. The
polymerizable group may be introduced into the molecule of the
cholesteric liquid crystal compound according to any of various methods.
The number of the polymerizable groups included in the polymerizable
cholesteric liquid crystal compound is preferably from 1 to 6, and more
preferably from 1 to 3. Examples of the polymerizable cholesteric liquid
crystal compound include those described in Makromol. Chem., Vol. 190, p.
2255 (1989), Advanced Materials, vol. 5, p. 107 (1993), U.S. Pat. No.
4,683,327B, U.S. Pat. No. 5,622,648B, U.S. Pat. No. 5,770,107B,
WO95/22586, WO95/24455, WO97/00600, WO98/23580, WO98/52905,
JP1989-272551A (JP-H1-272551A), JP1994-16616A (JP-H6-16616A),
JP1995-110469A (JP-H7-110469A), JP1999-80081A (JP-H11-80081A),
JP2001-328973A, and the like. The polymerizable cholesteric liquid
crystal compound may be used singly or in combination of two or more
kinds thereof. When the rod-like polymerizable liquid crystal compounds
are used in combination of two or more kinds thereof, the alignment
temperature may be lowered.

[0080] Moreover, the addition amount of the polymerizable cholesteric
liquid crystal compound with respect to the total mass of the
polymerizable cholesteric liquid crystal compound (A) and the
monofunctional monomer (C) in the polymerizable liquid crystal
composition is preferably from 50 to 99% by mass, more preferably from 70
to 98% by mass, and particularly preferably from 80 to 95% by mass, based
on the polymerizable liquid crystal composition.

[0081] Chiral Agent (Optically Active Compound):

[0082] The polymerizable liquid crystal composition is one exhibiting a
cholesteric liquid crystal phase, and accordingly, it includes a chiral
agent. In the invention, a chiral agent having an HTP of 50 μm-1
or less is used. The chiral agent may be selected from any known chiral
agents having an HTP of 50 μm-1 or less. (for example, chiral
agents used in TN and STN modes, described in Ekisho Debaisu Handobukku
(Liquid Crystal Device Handbook), 3rd Chapter, No. 4-3, p. 199,
edited by No. 142 Committee of Japan Society for the Promotion of
Science, published by the Nikkan Kogyo Shimbun, Ltd., in 1989. In the
invention, a chiral agent having an HTP of 45 μm-1 or less is
particularly preferably used, and a chiral agent having an HTP of 40
μm-1 or lower is further more preferably used.

[0083] Although, an optically-active compound generally has a chiral
carbon in its molecule, axially chiral compounds and planar chiral
compound, having no chiral carbon, may be used as a chiral compound in
the invention. Examples of the axially chiral compound or the planar
chiral compound include binaphthyl, helicene, paracyclophane and
derivatives thereof. The chiral agent may have a polymerizable group.
When the chiral agent has a polymerizable group, it is possible to form a
polymer having repeating units derived from a cholesteric liquid crystal
compound from the polymerization reaction of the polymerizable chiral
agent and the polymerizable cholesteric liquid crystal compound. In this
embodiment, the polymerizable group included in the polymerizable chiral
agent is preferably the same group as the polymerizable group included in
the polymerizable cholesteric liquid crystal compound. Accordingly, it is
preferably a polymerizable group contained in the chiral agent, an
unsaturated polymerizable group, an epoxy group, or an aziridinyl group,
more preferably an unsaturated polymerizable group, and particularly
preferably an ethylenically unsaturated polymerizable group.

[0084] Further, the chiral agent may be a liquid crystal compound.

[0085] The content of the chiral agent in the polymerizable liquid crystal
composition is preferably from 1 to 10% by mass with respect to the
polymerizable cholesteric liquid crystal compound used in combination
therewith. Further, the content of the chiral agent in the polymerizable
liquid crystal composition is more preferably from 1 to 24% by mass, and
particularly preferably from 1 to 18% by mass, with respect to the
polymerizable liquid crystal compound. In addition, the addition of the
chiral agent in the polymerizable liquid crystal composition is
preferably from 1 to 18% by mass, more preferably from 1 to 12% by mass,
and particularly preferably from 1 to 7.8% by mass, with respect to the
total mass of the polymerizable cholesteric liquid crystal compound (A)
and the monofunctional monomer (C) in the polymerizable liquid crystal
composition.

[0086] Monofunctional Monomers:

[0087] The polymerizable liquid crystal composition used in the invention
includes a monofunctional monomer in order to increase the brittleness of
the infrared light-reflecting film. In the present specification, the
monofunctional monomer refers to a compound having one polymerizable
group. The monofunctional monomer that is used in the invention is not
limited as long as it is a compound having one polymerizable group. The
monofunctional monomers may be used singly or in combination of two or
more kinds thereof, if desired.

[0088] Hereinafter, specific examples of the monofunctional monomer that
can be used in the invention are shown below, but the invention is not
limited to such specific examples. Further, the monofunctional monomer
that can be used in the invention preferably has a structure of a
(meth)acrylate among the following specific examples, and more preferably
has a structure of a monofunctional alkyl (meth)acrylate.

<<Compound Examples of (Meth)Acrylates>>

[0089] In the invention, the "(meth)acrylate" refers to an acrylate or a
methacrylate. Further, the "(meth)acryloyloxy" means acryloyloxy or
methacryloyloxy.

[0110] The addition amount of the monofunctional monomer in the
polymerizable liquid crystal composition is preferably from 1.8 to 30% by
mass, more preferably from 2 to 30% by mass, even more preferably from 2
to 27% by mass, particularly preferably from 2.7 to 20% by mass, and most
preferably from 4.5 to 9% by mass, with respect to the total amount of
the polymerizable cholesteric liquid crystal compound (A) and the
monofunctional monomer (C) in the polymerizable liquid crystal
composition.

[0113] In the production method of the invention, one kind or two or more
kinds of organic solvent can be used, and two or more kinds of organic
solvent are preferably used.

[0114] Furthermore, from the viewpoints of the solubility of the solid
contents and the efficiency of drying the coated film, an organic solvent
having a boiling point under standard conditions (normal temperature
(25° C.) and normal pressure) of 150° C. or higher is
preferably used, an organic solvent having a boiling point of 150°
C. or higher and 200° C. or lower is more preferably used, and an
organic solvent having a boiling point of 150° C. or higher and
190° C. or lower is particularly preferably used. In addition, an
organic solvent having a boiling point of 150° C. or higher is
preferably added in an amount of 2% by mass to 30% by mass, more
preferably in an amount of 4% by mass to 20% by mass, and particularly
preferably in an amount of 5% by mass to 10% by mass, with respect to the
total amount of the organic solvent. Herein, it is generally thought that
the amount of the eluate eluting from the coated film is increased by
increasing the amount of the residual solvent after the alignment step,
and thus, if the amount of water in the solvent is increased, the
alignment of the liquid crystal is deteriorated. As a result, adjustment
of the amount of the residual solvent to a high value of 0.20 g/m2
or more as in the invention cannot be usually employed in the case of
forming a film by coating a liquid crystal layer. Particularly, it is
thought that since in the case where two or more layers, and preferably
three or more layers, for the purpose of extending the reflection
wavelength band, of the coated film of the polymerizable liquid crystal
composition are laminated in order to reflect left-handed circular
polarization and right-handed circular polarization at once as in a
preferable embodiment of the invention, the eluate is generated at each
coating step, and as a result, a risk of the increase in the amount of
the eluate is increased when the residual solvent is increased.
Therefore, adjusting the amount of the residual solvent to a high value
of 0.20 g/m2 or more as in the invention even in the case of
producing a film with one layer of the liquid crystal layer has not been
substantially investigated. Particularly, it has been thought that it is
not necessary to conduct an investigation in an optically reflective film
using a cholesteric liquid crystal phase which is required to reflect
left-handed circular polarization and right-handed circular polarization
at once or to extend a narrow reflection wavelength band. Contrary to
these findings, in the invention, the alignment of the liquid crystal is
improved and the haze can be further improved even when a chiral agent
having a low HTP is used as a polymerizable liquid crystal composition
component and a monofunctional monomer for improving the brittleness is
added by increasing the amount of the residual solvent of the organic
solvent (D) after the alignment step in the polymerizable liquid crystal
composition. Particularly, this effect is apparent when an organic
solvent having a boiling point of 150° C. or higher is at least
included as an organic solvent (D) in the polymerizable liquid crystal
composition. The reason therefor is not clear and not restricted to any
theory, but the present inventors have speculated as follows. It is
thought that when a coating liquid of a polymerizable liquid crystal
composition for an upper layer containing a large amount of a solvent is
coated on a lower layer that is an infrared light-reflecting layer, the
polymerizable liquid crystal composition for an upper layer cannot easily
dissolve the lower layer by a mechanism described in the alignment step
or the like in the present specification, and thus, the effect of the
invention is enhanced. Among these, in a more preferable embodiment of
the invention, by adding an organic solvent having a specific structure
as described later, an organic solvent having a high boiling point, in
which the boiling point is within a specific range, or the like to the
polymerizable liquid crystal composition, there is a further effect on an
SP value or the like, and thus, the effect of the invention is further
enhanced. The organic solvent having a boiling point of 150° C. or
higher, that is used in the invention, is preferably a compound having a
hydrocarbon ring in the form of a 6- to 7-membered ring. The hydrocarbon
ring may further have a substituent and examples of the substituent
include a quinone group (═O), a hydroxyl group, an alkyl group
(preferably having 1 to 3 carbon atoms), a halogen atom (preferably a
chlorine atom), and the like. Among the hydrocarbon rings of a 6- to
7-membered ring, specifically, preferable examples include cyclohexanone,
cyclohexanol, dichlorobenzene, trimethylbenzene, chlorotoluene, and the
like. In addition, the organic solvent that is used in the invention is
more preferably a compound having a hydrocarbon ring of a 6-membered
ring, and particularly preferably cyclohexanone or cyclohexanol. From the
viewpoints of a coating film-forming property, production efficiency, or
the like, the addition amount of the organic solvent in the polymerizable
liquid crystal composition is preferably from 50% by mass to 80% by mass,
and more preferably from 40% by mass to 70% by mass.

[0115] Alignment-Control Agent:

[0116] Preferable examples of the alignment control agent that can be used
in the invention include compounds represented by the following general
formulae (I) to (IV). Two or more kinds selected from these compounds may
be used in combination. The compounds may contribute to aligning the
molecules of the cholesteric liquid crystal compound with a reduced tilt
angle or substantially horizontally at the air-interface alignment of the
infrared light-reflecting layer.

[0117] Further, it is to be understood that the term "horizontal
alignment" in the present specification means that the direction of long
axis of a liquid crystalline molecule is parallel to the layer plane,
wherein being strictly parallel is not always necessary; and means, in
this specification, that a tilt angle of the mean direction of long axes
of the liquid crystalline molecules with respect to the horizontal plane
is smaller than 20°. The layer in which liquid crystal molecules
are horizontally aligned at the air-interface may hardly suffer from
alignment defects, and may have a high transparency for visible light and
have a high reflectacne. On the other hand, the layer in which the liquid
crystal molecules are aligned with a large tilt angle may suffer from the
finger-print pattern, and may have a low reflectacne, a high haze, and
diffraction characteristics, because of the misalignment between the
helical axis of the cholesteric liquid crystal phase and the normal line
of the layer surface.

##STR00001##

[0118] In the formulae, a plurality of R's are the same as or different
from each other and represent an alkoxy group having 1 to 30 carbon
atoms, preferably 1 to 20 carbon atoms, and more preferably 1 to 15
carbon atoms, which may be substituted with a fluorine atom. One or more
CH2 or two or more CH2, which are not adjacent to each other,
in the alkoxy group may be substituted with O, S, OCO--, --COO--,
--NRa--, --NRaCO--, --CONRa--, --NRaSO2--, or
--SO2NRa--. Ra represents a hydrogen atom or an alkyl
group having 1 to 5 carbon atoms. By substituting R with one or more
fluorine atoms, the alignment control agents are highly distributed and
localized at the air-interface of the light-reflecting layer, and elute
and diffuse into the upper layer easily. The compound having a terminal
carbon atom substituted with a fluorine atom is preferable; and the
compound having a perfluoroalkyl group at the terminal is more
preferable.

[0125] In the formulae, n, n1, and n2 represent an integer of equal to or
more than 1, respectively; n is preferably from 1 to 20, or more
preferably from 5 to 15; n1 is preferably from 1 to 10, or more
preferably from 1 to 5; and n2 is preferably from 1 to 10, or more
preferably from 2 to 10.

[0126] In the formulae, m1, m2, and m3 represent an integer of equal to or
more than 1 respectively.

[0127] In the formula, m1 is preferably 1 or 2, or more preferably 2. When
m1 is 1, it preferably links to the para-position; and when m1 is 2, R's
preferably link to the para- and meta-positions.

[0128] In the formula, m2 is preferably 1 or 2, or more preferably 1. When
m1 is 1, it preferably links to the para-position; and when m1 is 2, R's
preferably link to the para- and meta-positions.

[0129] In the formula, m3 is preferably from 1 to 3; and R's preferably
links to two meta-positions and one para-position with respect to the
position of --COOH.

[0130] Examples of the compound represented by the formula (I) include
those described in paragraphs [0092]-[0093] of JP2005-99248A.

[0131] Examples of the compound represented by the formula (II) include
those described in paragraphs [0076]-[0078] and paragraphs [0082]-[0085]
of JP2002-129162A.

[0132] Examples of the compound represented by the formula (III) include
those described in paragraphs [0094]-[0095] of JP2005-99248A.

[0133] Examples of the compound represented by the formula (IV) include
those described in paragraph [0096] of JP2005-99248A.

[0134] The amount of the alignment control agent to be used is preferably
from 0.01 to 20% by mass, and more preferably from 0.02 to 8% by mass,
with respect to the polymerizable cholesteric liquid crystal compound
(solid contents in the case of the coating liquid).

[0137] The content of the photopolymerization initiator used is preferably
from 0.1 to 20% by mass, and more preferably from 1 to 8% by mass, with
respect to the polymerizable cholesteric liquid crystal compound (the
solid content in the case of the coating liquid).

[0138] Other Additives:

[0139] In addition, the liquid crystal composition may include at least
one additive selected from various additives such as an anti-unevenness
agent, an anti-repelling agent, a polymerizable monomer, and the like so
as to improve the uniformity of alignment, the coating property, or the
film strength. Further, if necessary, the liquid crystal composition may
contain any polymerization inhibitor, an antioxidant, an ultraviolet
absorber, a light-stabilization agent, a coloring material, fine
particles of metal oxide, or the like in an amount unless the optical
properties of the infrared light-reflecting layer are lowered.

[0140] (Substrate)

[0141] The substrate that is used in the method of producing an infrared
light-reflecting film of the invention is not particularly limited. An
infrared light-reflecting layer is formed on any substrate, and thus, the
infrared light-reflecting film of the invention can be produced. As the
substrate, for example, a polymer film, a glass plate, a quartz plate,
and the like, and a polymer film having high transmission to visible
light is preferably used.

[0142] Examples of the polymer film having high transmission to visible
light include polymer films used for various optical films that are used
as a member of display devices such as a liquid crystal display device
and the like. As the polymer film for an optical film, polyester films
such as polyethylene terephthalate (PET), polybutylene naphthalate, and
polyethylene naphthalate (PEN) films, and the like; polycarbonate (PC)
films; polymethylmethacrylate films; polyolefin films such as
polyethylene and polypropylene films, and the like; polyimide films,
triacetyl cellulose (TAC) films are preferable, polyethylene
terephthalate films and triacetyl cellulose films are more preferable,
and polyethylene terephthalate films are particularly preferable.

[0143] [Infrared Light-Reflecting Film]

[0144] The infrared light-reflecting film of the invention is produced by
the method of producing an infrared light-reflecting film of the
invention, wherein the film preferably reflects infrared light at a
wavelength of 800 nm or more, and more preferably light in a wavelength
region reflecting 30% or more of the incident light in the infrared light
region at 800 nm to 2000 nm. Hereinbelow, the light-reflecting film of
the invention will be described.

[0145] (Configuration)

[0146] Examples of the infrared light-reflecting film produced through the
use of the production method according to the invention are shown in
FIGS. 1 and 2, respectively.

[0147] An infrared light-reflecting film 21 shown in FIG. 1 has an
infrared light-reflecting layer 14b constituted by fixing a cholesteric
liquid crystal phase on the surface on one side of a resin film 12.
Further, infrared light-reflecting film 21 as shown in FIG. 2 further has
infrared light-reflecting layers 14a, 16a, and 16b constituted by fixing
a cholesteric liquid crystal phase thereon. The infrared light-reflecting
film of the invention is not limited to such embodiments, and in a
preferable embodiment, 3 or more infrared light-reflecting layers are
formed, and in a more preferable embodiment, 6 or more infrared
light-reflecting layers are formed.

[0148] In the infrared light-reflecting film 21 shown in FIGS. 1 and 2,
respectively, the cholesteric liquid crystal-containing infrared
light-reflecting layer immobilizes a cholesteric liquid crystal phase
therein, and therefore, the infrared light-reflecting film 21 exhibits
light selective reflection of reflecting a light having a specified
wavelength on the basis of a helical pitch of the cholesteric liquid
crystal phase. For example, when the adjacent light-reflecting layers
(14a and 14b, or 16a and 16b) have a helical pitch of the same degree and
exhibit an optical activity in a reverse direction to each other, any of
left-handed and right-handed circular polarizations of a wavelength of
the same degree can be reflected, and hence, such is preferable. For
example, as an example of the infrared light-reflecting film 21 shown in
FIG. 2, there is exemplified an example in which in the light-reflecting
layers 14a and 14b, the light-reflecting layer 14a is composed of a
liquid crystal composition containing a dextrorotatory chiral agent,
whereas the light-reflecting layer 14b is composed of a liquid crystal
composition containing a levorotatory chiral agent, and the
light-reflecting layers 14a and 14b have a nearly-equal helical pitch.

[0149] In another example of the infrared light-reflecting film 21 shown
in FIG. 2, the relationship between the infrared light-reflecting layers
14a and 14b are the same as in the above-mentioned example of the
infrared light-reflecting film 21 (both helical pitches are d14 nm), the
infrared light-reflecting layer 16a is formed of a curable liquid crystal
composition containing a dextrorotatory chiral agent, the infrared
light-reflecting layer 16b is formed of a curable liquid crystal
composition containing a levorotatory chiral agent, the helical pitches
in the infrared light-reflecting layers 16a and 16b are nearly equal
(both helical pitches are d16 nm), and a condition d14≠d16 is
satisfied. The infrared light-reflecting film 21 satisfying these
conditions achieves the same advantages as the example of the infrared
light-reflecting film 21 and the wavelength band of light to be reflected
by the infrared light-reflecting layers 16a and 16b expands, thereby
exhibiting a wide-band light-reflecting property. The invention is not
limited to the even number of infrared light-reflecting layers, but an
odd number of layers may be formed.

[0150] The infrared light-reflecting film produced through the use of the
production method according to the invention exhibits a selective
reflection characteristic based on the cholesteric liquid crystal phases
of the respective layers. The infrared light-reflecting film according to
the invention may have an infrared light-reflecting layer in which one of
right-twisted and left-twisted cholesteric liquid crystal phases is
fixed. When the infrared light-reflecting layers in which the
right-twisted and left-twisted cholesteric liquid crystal phases of the
same helical pitches are fixed are formed, the selective reflectance of
light of a specific wavelength increases, which is preferable. When
plural pairs of infrared light-reflecting layers in which the
right-twisted and left-twisted cholesteric liquid crystal phases of the
same helical pitches are fixed are formed, it is possible to raise the
selective reflectance and to widen the selective reflection wavelength
region, which is preferable. Incidentally, the rotation direction of the
cholesteric liquid crystal phase can be adjusted by the use of the kinds
of the rod-like liquid crystal compound or the kinds of the chiral agent
to be added, and the helical pitch can be adjusted by the use of the
concentrations of the materials.

[0151] (Characteristics)

[0152] The total thickness when the infrared light-reflecting film is a
stacked body having two or more light-reflecting layers is not
particularly limited. However, in the configuration in which the infrared
light-reflecting film includes four or more infrared light-reflecting
layers in which a cholesteric liquid crystal phase is fixed and exhibits
the light-reflecting characteristic over the infrared light region, that
is, in the configuration in which the infrared light-reflecting film
exhibits the heat-shielding property, the thickness of each infrared
light-reflecting layer is in the range of 3 to 6 μm and the total
thickness of the light-reflecting film is generally in the range of 15 to
40 μm.

[0153] Moreover, the selective reflection wavelength of one infrared
light-reflecting layer (each infrared light-reflecting layer in the case
where the infrared light-reflecting film includes plural infrared
light-reflecting layers) of the infrared light-reflecting film according
to the invention is not particularly limited. By adjusting the helical
pitch depending on its application, it is possible to give the reflection
characteristic for light of a desired wavelength. For example, at least
one infrared light-reflecting film can be provided which is a so-called
infrared light-reflecting film reflecting a part of light in the infrared
light wavelength region of 800 nm to 2000 nm. This infrared
light-reflecting film exhibits the heat-shielding property. Another
example of the infrared light-reflecting film according to the invention
is an infrared light-reflecting film which can reflect 80% or more (more
preferably 90% or more) of solar rays in the wavelength range of 900 nm
to 1160 nm. When a window film is produced using this infrared
light-reflecting film, it is possible to achieve high heat-shielding
performance in which the shielding factor defined in JIS A-5759 (a film
for a construction glass window) is 0.7 or less.

[0154] With the infrared light-reflecting film of the invention, a low
haze can be attained, and specifically, the haze of the infrared
light-reflecting film can be adjusted to less than 0.30%. The infrared
light-reflecting film of the invention includes a chiral agent having an
HTP represented by the following Expression (1) of 50 μm-1 or
less. Further, the haze of the infrared light-reflecting film is 0.50% or
less, more preferably 0.40% or less, and particularly preferably 0.30% or
less. In addition, it is preferable that the haze satisfy the preferred
range as described above and the brittleness (elongation at break) as
described later of the infrared light-reflecting film be 2% or more.

[0155] The infrared light-reflecting film that is used as attached onto
windows or the like is required to be transparent, and a lower haze
thereof is preferred. The haze is preferably 0.30% or less. Further, the
haze is measured in accordance with JIS K 7136:2000 (method for
determining the haze of a plastic-transparent material).

[0156] (Brittleness)

[0157] It is preferable that the haze of the infrared light-reflecting
film of the invention have good brittleness. Particularly, when used in
window members of vehicles or window members of building structures, it
is preferable that the infrared light-reflecting film have good
brittleness. The infrared light-reflecting film of the invention
preferably has an elongation at break, as measured by the following
method, of 2% or more, more preferably 4% or more, and particularly
preferably 6% or more. The brittleness (elongation at break) in the
invention can be determined by adding increasing load on a sample,
measuring the growth at break, and calculating the elongation relative to
the original length.

[0158] (Shape)

[0159] The infrared light-reflecting film according to the invention may
have a sheet-like spread shape or a shape wound on a roll, and preferably
has a shape wound on a roll. The infrared light-reflecting film according
to the invention can maintain excellent optical characteristics even when
the winding and the delivery are repeated in the production process, and
can also maintain excellent optical characteristics even when it is
stored or transported in the state where the produced light-reflecting
film is wound on a roll.

[0160] The infrared light-reflecting film according to the invention may
be a member having such a self-supporting property that it can be used as
a window material or may be a member not having a self-supporting
property but being bonded to a substrate such as a glass plate having a
self-supporting property.

[0161] When the cholesteric liquid crystal phase is fixed, any one of a
right-handed circular polarization component and a left-handed circular
polarization component is fixed on one layer, and accordingly, the
infrared light-reflecting film having one infrared light-reflecting layer
exhibits 50% reflection performance to the maximum. By repeatedly
laminating a layer reflecting the right-handed circularly-polarized light
component and a layer reflecting the left-handed circularly-polarized
light component, it is possible to enhance the reflection performance up
to 100% to the maximum. The width of the reflection wavelength band is
generally in the range of 100 to 150 nm, but the reflection wavelength
band can be widened to the range of 150 to 300 nm by using a material
having high birefringence Δn in the cholesteric liquid crystal
phase or adjusting the chiral agent concentration distribution in the
film section direction of the chiral agent in the produced infrared
light-reflecting layer.

[0162] (Usage)

[0163] The usage of the infrared light-reflecting film of the invention is
not particularly limited, but the infrared light-reflecting film is
preferably used in window members of vehicles or window members of
building structures.

[0164] The infrared light-reflecting film according to the invention may
be used in the state where it is bonded to the surface of a glass plate
or a plastic substrate. In this case, the bonding surface of the
light-reflecting film to the glass plate or the like preferably has an
adhesive property. In this embodiment, the infrared light-reflecting film
according to the invention preferably has an adhesive layer or a
highly-adhesive layer which can be bonded to the surface of a substrate
such as a glass plate. The non-adhesive infrared light-reflecting film
according to the invention not including an adhesive layer or a
highly-adhesive layer may be bonded to the surface of a glass plate with
an adhesive agent.

[0165] The infrared light-reflecting film according to the invention
preferably exhibits the heat-shielding property with respect to solar
rays and preferably efficiently reflects the infrared rays of 700 nm or
greater in solar rays.

[0166] The infrared light-reflecting film according to the invention can
be used as a heat-shielding window itself for a vehicle or a building or
can be used as a sheet or film to be bonded to a window of a vehicle or a
building. In addition, the film according to the invention can be used on
a freezer showcase, as an agricultural house material, an agricultural
reflecting sheet, and a solar cell film. Among those, the infrared
light-reflecting film according to the invention can be preferably used
as a window-attaching infrared light-reflecting film, in view of
characteristics such as high transmittance of visible rays and a low
haze.

[0167] Furthermore, the infrared light-reflecting film of the invention
may be attached to the inside of reinforced glass and used as a member of
a heating-shielding member.

[0168] The heat-shielding member is bonded as a solar ray shielding member
to windows of buildings such as houses or office buildings or vehicles
such as cars. Alternatively, the infrared light-reflecting film according
to the invention can be used as a solar ray shielding member itself (for
example, as a heat-shielding glass or a heat-shielding film).

EXAMPLES

[0169] Hereinbelow, the features of the invention will be described in
more detail with reference to Examples and Comparative Examples (where
the comparative example is not a known technique). The materials, use
amounts, ratios, process details, process sequences, and the like shown
in Examples below may be appropriately modified without departing from
the spirit of the invention. Accordingly, the scope of the invention
should not be construed to be limited to the specific examples shown
below.

[0170] The compounds that are used in Examples or Comparative Examples
will be described below.

[0206] First, a coating liquid having the composition of Example 1 shown
in Table 1 below was prepared.

[0207] (Coating, and Film Formation)

[0208] The prepared coating liquid was coated onto the surface of a PET
film having a thickness of 50 μm, manufactured by FUJIFILM, at room
temperature using a wire bar so as to have a thickness of the dried film
of about 4 to 5 μm;

[0209] the film was dried at 30° C. for 30 seconds, and then heated
in an atmosphere at 100° C. for 2 minutes to form a cholesteric
liquid crystal phase; and

[0210] subsequently, controlling the output of the lamp using a metal
halide lamp manufactured by Eye Graphics at 30° C., this was
irradiated with UV rays in a nitrogen-purged atmosphere at a dose of 28.3
mW/cm2 for 3 seconds to fix the cholesteric liquid crystal phase and
to form an infrared light-reflecting film of Example 1. Further, the
amount of the residual solvent after the drying step ((the amount of the
residual solvent after the drying step)=(the mass after drying step)-(the
mass after drying at 130° C. for 30 minutes)) was measured, and as
a result, the amount of the residual solvent was 0.433 g/m2. In
addition, the amount of the residual solvent after the alignment step to
give a cholesteric liquid crystal phase was measured in accordance with
the method described in the present specification, and as a result, the
amount of the residual solvent was 0.264 g/m2.

Examples 2 to 14 and Comparative Examples 1 to 4

[0211] In the same manner as in Example 1 except that the coating liquid
was changed as shown in Table 1 below, infrared light-reflecting films of
Examples and Comparative Examples were formed. Further, the addition
amounts of the respective components in Table 1 below are based on mass.

[0212] (Haze of 7 Laminated Layers)

[0213] When the alignment of the cholesteric liquid crystal phase is
deteriorated, the reflection rate is lower and the haze increases
remarkably, and thus, as an index of the alignment property of the
cholesteric liquid crystal phase, the total haze of the infrared
light-reflecting film was measured. The haze was measured in accordance
with JIS K 7136:2000 (method for determining the haze of
plastic-transparent materials). [0214] A: Haze of 0.20% or more and
less than 0.30% [0215] B: Haze of 0.30% or more and less than 0.40%
[0216] C: Haze of 0.40% or more and less than 0.50% [0217] D: Haze of
0.50% or more and less than 0.70% [0218] E: Haze of 0.70% or more

[0219] The infrared light-reflecting film rated C or higher can be
practically used.

[0220] The obtained results are shown in Table 1 below.

[0221] Herein, the haze was measured in an embodiment in which seven
infrared light-reflecting layers (cholesteric liquid crystal phase) were
laminated on a resin film. Specifically, the first infrared
light-reflecting layer was laminated on the resin film by the method
above, and subsequently, 2 to 7 layers were laminated by the same method.
Further, the types and the addition amounts of the polymerizable
cholesteric liquid crystal compounds, the monofunctional monomers, and
the chiral agents used in the first to seventh layer in the respective
Examples and Comparative Examples were the same as each other, but the
addition amount of the alignment control agent F in the first layer was
adjusted to 0.03 parts by mass, whereas the addition amount of the
alignment control agent F in the second or higher layer was adjusted to
0.01 parts by mass.

[0222] (Brittleness)

[0223] By a Tensilon tensile tester, tension was applied on a sample of
100 mm×10 mm (infrared light-reflecting film) while applying a
load, and the elongation at break and the brittleness (elongation at
break) were measured. The obtained results are shown in Table 1 with
elongation at break (expressed as a percentage).

[0224] From Table 1, it was found that by using the method of producing an
infrared light-reflecting film of the invention, an infrared
light-reflecting film having excellent brittleness as well as a low haze
even when a chiral agent having a low HTP is used can be produced.

[0225] On the other hand, from Comparative Examples 1 to 3, it was found
that when the amount of the residual solvent after the alignment step is
below the range of the invention, the haze becomes higher.

[0226] In addition, the peak of the reflection wavelength of the infrared
light-reflecting film obtained in each Example was 900 nm.

Example 15

[0227] In the same manner as in Example 1 except that the number of the
infrared light-reflecting layers was 3, an infrared light-reflecting film
was produced. With respect to the obtained infrared light-reflecting
film, the haze was measured by the same method as in Example 1. As a
result, even when the number of the infrared light-reflecting layers was
3, an infrared light-reflecting film having the same alignment as in
Example 1 was obtained.

Example 16

[0228] In the same manner as above except that the infrared
light-reflecting layer (also referred to as a first layer) laminated in
Example 1 was cooled to room temperature, and then the chiral agent (B-3)
for left-handed twisting used in Example 1 was changed to the chiral
agent (B-4) for right-handed twisting as described below, a second layer
was formed on the first layer of the infrared light-reflecting layers.
Further, the peak of the reflection wavelength of the light-reflecting
film after formation of the second layer was 1000 nm. In addition, in the
same manner as in Example 1 except that the chiral agent (B-3) for
left-handed twisting and the chiral agent (B-4) for right-handed twisting
were used alternately on the second layer after adjusting to such a
concentration that the peak of the reflection wavelength was 1120 nm, the
third layer and the fourth layer were laminated. Subsequently, in the
same manner, as in Example 1 except that the chiral agent (B-3) for
left-handed twisting and the chiral agent (B-4) for right-handed twisting
were used alternately thereon after adjusting to such a concentration
that the peak of the reflection wavelength was 1240 nm, thereby forming a
fifth layer and a sixth layer.

[0229] The obtained light-reflecting film has the same tendency as in
Example 1.